The Home Office's real-time public display gives energy waste no place to hide. Graphic: Home Office

"There can be no hiding place for energy waste in central government," said Chris Huhne, the climate secretary, at today's launch of a new real-time public display of how much electricity and gas his department is using.

At 4.41pm this afternoon, the Decc display was running at 302 watt hours per hour, which generated 165.8kg of carbon dioxide, and cost £24.76. On their own, the figures hold a kind of momentary fascination, but are essentially meaningless. Below, however, is a link to "learn more about this" where we discover that in the previous year to the end of March the department cut its energy use by nigh on 30%, and emissions (gas was cut more than electricity and has a lower carbon content) by almost 20%.

More interesting still is the main graphic graph for the past 24 hours: at teatime it's starts with a low patch in green, but just before it kicks up to the higher daytime figures in yellow and orange, and throughout the working day, there are about half a dozen sudden spikes sticking up high above the norm. A spokesman says the first spike, in the early hours of the morning, has been tracked back to the time the air-conditioning is programmed to switch on. Other spikes have not yet been identified, and more work is being done to study possible reasons, such as greater use of lifts around arrival, lunch and home times, said the spokesman.

Even more fascinating still is the Home Office graphic (see above) – harder to find via a link from a link on the department's website home page. This is a more basic model showing simply energy use for each of the last seven days. This time the most striking feature is the bizarrely low electricity and gas consumed on Friday of last week – even less than either of the weekend days following it. How could this be? Did the department generate lots of its own energy from solar panels on the roof that day? Did the computer network crash? Were a great many civil servants on half-term? This afternoon a Home Office spokesman said he could not find the right official to ask, and offered to respond on Friday. Watch this space...

What is the point of the exercise – which David Cameron has promised all departments will follow? It's partly to focus staff minds on the drive to cut energy use, partly to encourage the public to take an interest, and to be seen to be "walking the walk", says the Decc spokesman. "There can be no hiding place," as Huhne said. The Home Office – and others – have been warned.